1. Field of the Invention
The present invention relates to an evaporator for evaporating refrigerant of a refrigerant cycle and a method for manufacturing the evaporator. The evaporator is suitable for a vehicle air conditioner.
2. Related Art
U.S. Pat. No. 5,701,760 discloses a refrigerant evaporator by the applicant of the present invention. As shown in FIG. 20, an evaporator 100 has an upper inlet-side tank 50, a lower inlet-side tank 51, an upper outlet-side tank 52 and a lower outlet-side tank 53. The upper inlet-side tank 50 and the upper outlet-side tank 52 are disposed at an upper end of the evaporator 100, and the lower inlet-side tank 51 and the lower outlet-side tank 53 are disposed at a lower end of the evaporator 100. The evaporator 100 includes an inlet-side heat exchange portion X and an outlet-side heat exchange portion Y. The inlet-side heat exchange portion X is disposed on a downstream air side of the outlet-side heat exchange portion Y with respect to an air flowing direction A.
Further, the evaporator 100 has plural tubes through which refrigerant flows. Each of the tubes is formed by connecting a pair of metal thin plate having a bowl-like protruding portion at both longitudinal ends thereof. Each of the bowl-like protruding portions is integrally connected with each other, thereby forming the tanks 50-53.
As shown in FIG. 20, refrigerant is introduced into the evaporator 100 from an inlet 54a formed in a pipe joint 54 and flows into a first inlet-side tank portion 51a of the lower inlet-side tank 51 through a side passage 55. Then, refrigerant flows upwardly through a downstream-air-side passage I of the tubes and flows into the upper inlet-side tank 50. Refrigerant in the upper inlet-side tank 50 flows downwardly through a downstream-air-side passage II of the tubes and flows into a second inlet-side tank portion 51b of the lower inlet-side tank 51. Next, refrigerant flows from the second inlet-side tank portion 51b into a first outlet-side tank portion 52a of the upper outlet-side tank 52 through a side passage 56. Then, refrigerant flows downwardly through an upstream-air-side passage III of the tubes and flows into the lower outlet-side tank 53. Refrigerant in the lower outlet-side tank 53 flows upwardly through an upstream-air-side passage IV of the tubes and flows into a second outlet-side tank portion 52b of the upper outlet-side tank 52. Finally, refrigerant flows through a side passage 57 and is discharged to the outside of the evaporator 100 through an outlet 54b.
In the evaporator 100, the inlet-side heat exchange portion X is disposed on the downstream air side of the outlet-side heat exchange portion Y, and a flowing direction of refrigerant in the inlet-side heat exchange portion X corresponds to that in the outlet-side heat exchange portion Y. That is, in FIG. 20, refrigerant flows upwardly on a right side of partition members 58, 59 and flows downwardly on a left side of the partition members 58, 59 in both of the heat exchange portions X, Y. Therefore, even when liquid-gas two-phase refrigerant is biasedly distributed into the passages I-IV, air having an uniform temperature distribution is blown out from the evaporator 100. Further, refrigerant flows in a zigzag route through the passages I, II in the inlet-side heat exchange portion X and through the passages III, IV in the outlet-side heat exchange portion Y. As a result, heat amount absorbed by refrigerant is increased, thereby improving cooling performance of the evaporator 100.
However, the evaporator 100 requires the side passage 56 for a communication between the passage II and the passage III, and the side passages 55, 57 for a communication between the inlet 54a and the passage I and a communication between the passage IV and the outlet 54b. Each of the side passages 55-57 may be formed between two metal thin plates disposed on an end surface of the evaporator 100. As a result, the number of parts of the evaporator 100 is increased, thereby increasing production cost of the evaporator 100. Further, pressure loss of refrigerant in the evaporator 100 is increased due to the side passages 55-57. As a result, evaporation pressure and evaporation temperature of refrigerant in the evaporator 100 is increased, and cooling performance of the evaporator 100 is decreased.